A motor pump unit of the kind mentioned at the outset is described in DE 31 15 698 C1, for example. To protect the motor, a motor housing surrounding its rotor and stator in the form of a shell is provided. The heat of the motor can also be dissipated by way of the motor housing. A part of the suction line for cleaning liquid located upstream of the pump assembly forms a cooling channel for cooling the motor housing. DE 31 15 698 C1 proposes integrally forming the cooling channel as annular gap in the motor housing surrounding the motor. Alternatively, provision may be made to form the cooling channel as a helical tube embedded in the motor housing.
Motor pump units are also known in the prior art, in which the cooling channel is in the form of a cooling pot, through which the drawn-in cleaning liquid flows, and into which the motor housing projects.
The cleaning liquid is usually water, which may have a cleaning chemical added to it to increase the cleaning effect. The cleaning liquid may be so aggressive that in conventional motor pump units, as a result of corrosion of the walls of the cooling channel and, in particular, of the motor housing, it enters the interior thereof and, consequently, jeopardizes the electrical safety of the motor pump unit.
An object underlying the present invention is to provide a motor pump unit of the kind mentioned at the outset and a high-pressure cleaning appliance having a higher level of electrical safety than a conventional motor pump unit and a conventional high-pressure cleaning appliance, respectively.